Adding Ohm symbol to schematic

Schematic
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That is a great observation. But if we were to omit the units from all three types of passive components, would it lose any information? (I am biased; I am the odd guy out who uses engineering notation for component values.) I think that as long as base units (ohms, farads, and henries) are stipulated for the entire BOM, we do not really need any of those unit designators for the individual components.

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I guess it depends on what we’re used to seeing and personal preferences. I prefer seeing the unit symbol, but I get your point, it’s not strictly necessary. Heck, I still have to think twice when I see nF on a schematic. For some reason, most schematics when I was learning electronics skipped from pF to uF.

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I agree. I do not know why. To me it makes more sense to indicate 4.7 nF than 4700 pF or 0.0047 uF. And (maybe not today) I have seen separate redundant “values” listed at Mouser or Digikey. So one listing for 4700 pF and another for 4.7 nF or something like that


And a computer grade aluminum electrolytic capacitor would have been rated at 200,000 uF instead of 200 mF or 0.2F.

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I don’t entirely agree. Schematics are indeed made by engineers, but there are often different schematics prepared for different audiences. I think schematics should look pretty, because that helps not only in readability but in understanding. For example, arranging the signal flow from left to right goes a long way towards a better schematic in my experience. One project leader insisted that all connectors be shown on page one, a suggestion that annoyed me but I came to appreciate and adopt that style. I almost always make custom symbols for big items like MCUs or FPGAs in order to make the flow work for a project. I hate schematics that are nothing but parts with wire stubs and signal names. That’s not a schematic — that’s a graphical net list.

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I think that is a great post. I had a manager who would draw ground symbols pointing in all 4 directions. That always seemed counter-intuitive. I also believe in input towards the left and output towards right (for the most part.) I am not sure that any of these are matters of “pretty” though.

That is another great observation. I use local labels (in place of wires) sometimes but it makes the schematic more difficult to read.

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For good or bad reasons, ”F and pF were all that was used 30 years ago. Today if you talk to a machinist in hundredths of an inch (metric not withstanding) they will look at you like you have two heads.

That said there is nothing wrong with the term nF.

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The only thing that is constant is change. When I started playing with electronics, no one used picofarads, let alone nanofarads. Larger capacitors were in microfarads, and the tiny ones in “micro-micro-farads” or ””F. Picofarads came into common use later as a replacement for ””F. Nanofarads is an even more recent adoption.

Some years ago I took a 5 month assignment in Sweden. While cooking dinner one night I came upon a step in the recipe calling for “1 dl vatten”. Okay, “vatten” in Swedish translates to “water” in English. But it took me longer than I like to admit to realize that “dl” would be “deciliters”, an uncommon unit in the US where milliliters are more familiar.

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That would be a Micky Mike.

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So why are centimeters common but not centiliters? I am guessing something to do with the CGS system. I have the idea that nF might have become popular in Europe before USA, but

  1. SFAIK that is only a guess that Europeans did it first. Similarly I think it was some Europeans who invented French bread before Americans did. So much for American exceptionalism.

  2. Digikey’s listing of ceramic capacitors jumps from picofarads to microfarads.

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I have some old schematics from the 1970s for colour TVs published by Phillips.
The earliest was drawn then printed for a TV released in 1974 so it would be at least drawn 12 months earlier.
That has p, n & ” for capacitors and k & M for resistors
 no “R” is used.

BTW there are also a few four way junctions :grimacing:

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Your average person in the street here doesn’t know about CGS or even MKS. Metric and that’s it. Imperial is what some oldies still think in.

It’s more to do with length being used far more often in daily life. The most common units are km, for travel distances, e.g. biking, driving; m for lengths around the garden, in the built-up environment; cm for things in the house; mm for smaller things. There is a great deal of overlap; my bathroom tiles are 300x300 mm rather than 30x30 cm, maybe because the tile shop also has 15x15 mm mosaic tiles rather than 1.5x1.5 cm mosaic tiles.

For volume there is less need for lots of decade multiples, less so than in the past. Milk and petrol are purchased in litres; wine, beer and soft drinks in ml, l for larger bottles. Now and then you see a wine glass with a 15 cl mark, but people would rather say 150 ml of wine is one standard drink. For really large volumes writers resort to measures like an Olympic swimming pool (OSP). :wink:

Area is another one. Unlike volume, it’s often calcalated from lengths so units other than m^2 or cm^2 are rarely used. There is also of course the hectare, a non-SI unit.

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Weights (mass?) are pretty standard: either grams, kilos or tonnes
 SOME * people even know that 500gm = I/2 a kilo.

  • Note the word “some” (probably should read “a very few” :roll_eyes:)

But the tree in my new avatar has a span of just over 2 chains!

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Deciliter (dl) is a really common unit for cooking and baking here in Sweden!
It’s like everything in american recipies is measured in the unit ‘cup’.
Every kitchen has a small, usually stainless steel, ‘dl’ measure, that is used for measuring whatever you need for the cooking, unless it is salt and spices, then there are teaspoon and ‘kryddmĂ„tt’ which translates to ‘spice measure’ or similar


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Sometimes its marketing. Homes are still in square feet in Malysia, which has been metric for a very long time.
!000 sq ft sounds much bigger than 100 sq m

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Here in the US, food recipes drive me crazy. It would be so much easier in metric.

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In the British media the two accepted measurement units are “Seven or eight football pitches” and “Half the size of Wales” which, on reflection, are probably easier to grasp than “500 square miles” or “2 hectares”.

But you are right - in the building trade everything is mm (or metres) but never cm.

Now, it’s nearly going home time. Anyone fancy a pint?

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Recipes in metric are a pain if your measurement cups and spoons are in cups teaspoons and tablespoons. But an electronic kitchen scale is great. I use grams. Once you make the imperial volume measurement you can weigh it and measure grams in the future. By using tare function, you also reduce the amount of stuff needing to be washed later.

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Yes I can audiolise (? audio equivalent of visualise) in my mind my relatives saying sq ft in Chinese. It might partly be because a lot of pre-metric title deeds are in sq ft.

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Of course there are the informal units in some European countries cognate to “pound” which are 500g. NL and DE come to mind.

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@retiredfeline

My comment was about retail shopping in my area.
If the shop assistant is asked for 500gm of something, everything is OK and I will receive the amount asked for.
If I ask for 1/2 a Kilo, I am usually greeted with a look of stunned, uncomprehending amazement.

Mind you, I also get that stunned, uncomprehending look when I try to explain the sign over the express lane in the supermarket is just plain bad English and needs correcting.

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